"Four" signifies union, because it is made up of pairs, as also does two when it has relation to marriages of things (AC 720). But "five" signifies disunion, because it means but little (AC 649). The signification of all things is in accordance with the subject of which they are predicated.

The fourth generation signifies the same as forty and as four hundred; namely, the duration and the state of temptation, spoken of at (verse 13); it is a sort of diminutive from these. Whether a number be larger or smaller, provided it be of the same stock, it involves the same; as has already been stated several times. That the fourth generation does not signify any generation from Abram, or from Isaac, or from Jacob, is evident from the historicals of the Word; for there were more generations, and these people were very different from their fathers when they returned. The fourth generation is an expression that occurs likewise in other places, yet in the internal sense it never signifies any generation; and here it signifies the time and state of restoration, because it signifies the end of those things which are signified by forty or by four hundred (AC 862, 1847).

The four animals in the midst of the throne and round about the throne full of eyes before and behind are things of the understanding from the Divine in the heavens, four signifying their conjunction with the things of the will. For truths are of the intellectual part and goods are of the will part, whence it is said that they were full of eyes before and behind, because eyes signify things of the understanding, and hence in a higher sense the things of faith (AC 2701, 3820, 4403-4421, 4523-4534). Four denotes conjunction, the same as two, (AC 1686, 3519, 5194).